With the development of novel technology, various miniaturized handheld electrical apparatuses or wireless communication devices, such as mobile phones, laptop computers, personal digital assistants (PDAs), or wireless AP stations, are gradually popularized. To perform the wireless communication of the above handheld products, various small-sized antennas with good wireless communication performance are developed in order to operate under the standards for various different frequencies, such as IEEE 802.11a working at 5 GHz, IEEE 802.11b/g working at 2.4 GHz, IEEE 802.11n working at 5 and/or 2.4 GHz, Bluetooth working at 2.4 GHz and Worldwide Interoperability for Microwave Access (WiMAX) mainly working at 2.3, 2.5 and 3.5 GHz.
To meet the above demands, various different types of miniaturized antennas have been improved in the recent years. Although the improved antennas are able to operate at the above different frequencies and achieve high gain and optimal directivity, it is still expected to better strengthen structure solidity against the external force.
For example, the dual-band dipole antenna disclosed in U.S. Pat. No. 7,230,578 B2 controls the frequencies by the extending portions, the structure of which lacks support and may be deformed due to the external force although it is simple in structure and easy to be manufactured. The multi-mode and multi-band antenna with a combination of a helical and a pole antennas disclosed in U.S. Pat. No. 7,262,738 B2 enables the combination antenna to be tuned to three or more resonant frequencies, but it is concerned that the coil sections may be compressed by the external force and have negative impact on the working frequencies. The monopole-type antenna for multi- or wide-band use disclosed in U.S. Pat. No. 7,242,352 B2 has a feed conductor and bridge conductor respectively connected to two different top loading elements in order to produce two resonance modes, such that the antenna is applicable in a limited space and easy to be assembled. However, it is still concerned that the antenna with the elongated conductors is easy to be destroyed by the external force and has unstable assembling.
Conventional planar inverted-F antennas (PIFAs) have compact structure and good communication performance, such that they are widely applied to the wireless communication in various handheld electrical devices. In the conventional art, the coaxial cable for signal transmission has a core conductor and an external conductor respectively soldered to the feed point and the ground portion, so that the signal is thereby transmitted from a PIFA. However, the impedance matching and the frequency resonance of the antenna are impacted. Even an improved PIFA for solving the above mentioned problem, such as the dual-band antenna disclosed in U.S. Pat. No. 7,230,573 B2, still has extensive structures of radiation element portions, which lacks well support in structure, such that the configuration of the antenna is easy to be deformed due to the external force and not suitable for a portable communication device in a long term.
To meet business or entertainment demands, an user normally carries a handheld device in different occasions, so that the device is often impacted by the external force. Therefore, the above miniaturized antennas are not solid enough to avoid damages therefrom, and the signal transmitting/receiving performance may be influenced. Moreover, it is expected to make more efforts in achieving miniaturization of the antenna.
Therefore, to overcome the drawbacks from the prior art and to meet the present needs, the Applicant dedicated in considerable experimentation and research, and finally accomplishes the “dual-band antenna” of the present invention, which not only overcomes the above drawbacks regarding damages due to the external force but also present the space saving three-dimensional structure while still achieving good communication. The invention is briefly described as follows.